WO2001063580A1

WO2001063580A1 - Method and system for monitoring

Info

Publication number: WO2001063580A1
Application number: PCT/SE2001/000397
Authority: WO
Inventors: Patrik Lidberg
Original assignee: Vattenfall Ab
Priority date: 2000-02-25
Filing date: 2001-02-23
Publication date: 2001-08-30
Also published as: SE0000627D0; SE519259C2; AU3629601A; SE0000627L

Abstract

The present invention relates to a method and a system for monitoring a distribution board. In the distribution board, a characteristic binary parameter state which can assume a first and a second value, is detected in a contactless manner for at least one electric wire, whereby it is determined that detection of a change of state has occurred if the value of the binary parameter state is the first value, a first message about the detection being given.

Description

METHOD AND SYSTEM FOR MONITORING

Technical Field

The present invention relates to a method and system for monitoring a distribution board.

Technical Background

In large industrial premises which are provided with many electric units and complicated systems, it is necessary to obtain information if an electric fault has oc- curred. A useful source of information is, for example, a distribution board, in which it is possible to check if, for instance, a fuse has been blown. For, inter alia, time-saving reasons it is advantageous being able to remote monitor such a distribution board. Naturally, it may also be suitable to have the possibility of remote monitoring a distribution board or a fuse box in small facilities, such as in dwellings, which may also comprise a large number of power consuming units.

Summary of the Invention

The object of the present invention is to provide a method and a system for monitoring a distribution board, which are space-saving, uncomplicated and also inexpensive . This is achieved by obtaining, in a contactless manner, the desired measured values directly in the distribution board. The term "contactless" means that the measurement takes place in a non-galvanic manner, i.e. the electric conductor, on which it is desirable to measure, is not in direct contact with the measuring element.

This is very advantageous since it is often most inconvenient and, in some cases, also prohibited by law to carry out measurements in a distribution board by connecting a measuring line to an electric conductor, such as a fuse wire, which is available in the distribution board. Consequently, extension wires are generally laid from the wires available in the distribution board and are usually gathered in a box mounted adjacent to the distribution board, thus enabling the measurement to be carried out in the box instead.

It is thus a great advantage being able to carry out the measurement in a contactless manner directly on the distribution board since the extra space occupied by the box is saved. Other advantages of the measurement in a contactless manner have turned out to be the simple connecting method and the low costs.

In order to create favourable conditions for obtaining good measurements, it is advantageous if the parame- ter to be measured is representative of a binary parameter state which may assume two values. One value indicates that a fault has occurred, whereas the second value indicates that normal conditions prevail.

When it is discovered that the parameter has assumed the first value, a corresponding message may be sent, enabling necessary measures to be taken in order to restore the normal state. Similarly, a second message may be sent if the parameter has the second value, in order to confirm that normal conditions prevail . A suitable parameter as regards the present invention is the voltage across the electric wire or wires available in the distribution board, on which measurements are desirable. Provided that in the normal state there is a voltage across the wires, a failure message is sent if there is no voltage across the same.

Measurements on a wire in order to determine whether a voltage is present or not, are carried out preferably by capacitive measuring. For example, a conductive plate, which via a cable is connected to an amplifier circuit, may be arranged in the vicinity of the wire on which it is desirable to carry out measurements. Naturally, the expression "in the vicinity" also comprises the condition that the plate is applied, for example by adhesion, to the wire insulation. It is essential for the plate not to be in direct contact with the electric conductor in itself. The sensibility of the measurement varies, as is well known, with the area of the plate and the length of the cable connected to the plate. The sensibility is directly proportional to said area and in inverse proportion to said length. The plate does not need to be flat, but can also be bent in order to, for example, surround a wire. The design of the plate has to be considered in relation to what costs are reasonable in each individual case. A highly advantageous alternative to a plate is to use an electrically conductive tape which is attached to the cable and which is applied to the insulation of the wire, on which measurements are desirable. The cable connected to the amplifier circuit is preferably a microphone cable, i.e. it screens possible disturbance from other adjacent wires, on which measurements are not de- sirable by means of exactly that cable.

The inventive measurement in the distribution board can advantageously be used for discovering whether an electric fault relates to an incoming supply main of the distribution board or an outgoing main of the distribu- tion board. Measurement on an incoming supply main may thus indicate that a fault exists in one of the three incoming phases. Absence of voltage across an outgoing wire may indicate that at least one fuse in the distribution board has blown, whereas absence of voltage across an- other outgoing wire may indicate earth fault in at least one power consuming unit which is connected to the distribution board.

It should be understood from the above that in a distribution board a plurality of measuring units or sen- sors can advantageously be connected, which thus comprise a plate, a cable and an amplifier circuit. The plate (or alternatively tape or another means with a corresponding function) of each such sensor is applied to a specific wire. It is thus possible to have three sensors that perform measurements on the respective incoming phase wires. It is also possible to apply sensors in order to perform measurements on the wire of the earth fault breaker and the wires of the respective fuses in the distribution board.

The output signals from the respective amplifier circuits are preferably gathered in a common intermediate unit, in which the obtained information is processed and forwarded, preferably to a central processing unit which can inform the owner of the dwelling, the staff of the industrial premises or another user about what conditions are prevalent. The intermediate unit may be programmed to detect the sensors at suitable intervals and may also be programmed with conditional sentences that control output signals, if any. If, for example, the intermediate unit receives a signal which indicates that a special fuse has been blown, the intermediate unit may, as a consequence of this, forward the information to the central processing unit and suggest that also another fuse be turned off. Alternatively, in this example the intermediate unit may disconnect another fuse. The monitoring of the distribution board will be described in more detail in the following.

Brief Description of the Drawings

Fig. 1 schematically shows a system for monitoring a distribution board according to a preferred embodiment of the present invention.

Fig. 2 shows a circuit diagram of a preferred embodiment of a sensor for measuring voltage in a contactless manner in a wire in a distribution board according to the present invention. Fig. 3 schematically shows a preferred embodiment of an intermediate unit and its main components for use in the present invention.

Fig. 4 shows a flow chart of an intermediate unit for monitoring a distribution board according to the present invention.

Fig. 5 shows a flow chart of a server for monitoring a distribution board according to the present invention.

Description of Preferred Embodiments

Fig. 1 schematically shows a system for monitoring a distribution board 2 according to a preferred embodiment of the present invention. The distribution board 2 comprises a set of wires 4a-4j , the status of each wire be- ing intended for monitoring. A sensor 5a-5j for measuring voltage in a contactless manner is connected to each wire 4a-4j , on which measurements are to be performed. The sensors 5a-5j communicate via signal lines 7a-7j with an intermediate unit 10, in which the obtained information is processed.

The intermediate unit 10 communicates with a central processing unit or a server 12 via a network 14, the server 12, in its turn, also communicating with an alarm unit 16, such as a visual display, a computer, a tele- phone, an acoustic indicator, etc.

A chip in the intermediate unit 10 is programmed for communicating with the sensors 5a-5j . The software in the chip determines how often the sensors 5a-5j are to be polled. In this software it is also possible to add a certain logic in such a manner that the intermediate unit 10, by itself, can come to a decision. The intermediate unit 10 communicates, for instance, via LonWorks . The protocol that is used is LonTalk® .

The program in the server 12 polls the intermediate unit 10 what parameter state prevails for each wire 4a- 4j , which the intermediate unit 10 has obtained from the sensors 5a-5j and stored. If the server 12 detects such a value that indicates absence of voltage across one of the wires 4a-4j , the alarm is given. The alarm may be sent to the alarm unit 16, for example, by means of prior-art computer network technique . As illustrated in the Figure, six sensors 5a-5f are connected to an earth fault breaker 20 that is available in the distribution board 2. Of these the three upper sensors 5a-5c are connected to incoming supply main wires 4a-4c for obtaining information whether the three incom- ing phases in the house have voltage. The three lower sensors 5d-5f are connected to outgoing wires 4d-4f and give information about an earth fault, if any. Thus, the system can distinguish an incoming phase error from an incoming earth fault. Furthermore, the Figure shows four sensors 5g-5j which are connected to one outgoing wire 4g-4j each. Measurements on these gives information whether a fuse 22, 24, 26, 28 has blown. Of course, measurements on several fuses can be performed. However, for the sake of clarity, only four are shown. Although Fig. 1 shows a server 12 which polls the intermediate unit 10 and conveys the information to an alarm unit 16, it is possible to completely eliminate the server 12. In that case, the intermediate unit 10 gives information directly to an alarm unit 16, such as a vis- ual display in the form of a matrix with light-emitting diode bars or an LCD .

Fig. 2 shows a circuit diagram of a preferred embodiment of a sensor 5 for measuring voltage in a contactless manner on a wire in a distribution board accord- ing to the present invention. The sensor 5 comprises a sensor surface in the form of a conducting plate 30. The conducting plate 30 is intended for being fixed with tape on the surrounding insulation of an electric wire available in a distribution board. From the plate 30 runs a signal cable 32 in the form of a microphone cable which screens possible disturbance from other adjacent wires. The screening is connected to zero potential. The capaci- tance of the sensor surface 30 and the capacitance of the signal cable 32 thus form a capacitive voltage divider which transmits the alternating current signal from the wire to a first amplifier step FI which amplifies the signal and forwards it to a second amplifier step F2 which converts the signal to a square wave. The square wave then passes a high-pass filter which consists of a capacitor Ci and a resistor R_x . The high-pass filter bars direct voltage, but lets through the square wave. The signal then continues to a third amplifying step F3 which serves as a buffer step, which forwards the signal to subsequent electronic units. Thus, the presence of a "square wave" from the sensor 5 is a measure of voltage being present across the wire, whereas absence of a "square wave" from the sensor 5 is a measure of the wire being dead.

The Figure also shows a resistor R₂ across the first amplifier step FI . The resistor determines the operating point on the amplifier step and has suitably a resistance of 10 MΩ. Moreover, a diode Di is shown in the Figure.

The diode serves as a clipper diode and locks the signal to the zero potential.

Fig. 3 schematically shows a preferred embodiment of an intermediate unit 40 and its main components for use in the present invention. The intermediate unit 40 obtains its power supply from an external power supply source 42. The source 42 communicates with a chip 44 by a power supply wire 46. The chip 44 has software for obtaining parameter values and storing them in a memory to be forwarded to a server via a signal output 48. The chip furthermore has 16 sensor inputs 50a-50p for connecting sensors for measuring voltage in a contactless manner on a wire in a distribution board. Ten of the sensor inputs 50g-50p are adapted to detect that a fuse has blown, three inputs 50a-50c to detect incoming phase errors and three inputs 50d-50f to detect earth faults. Fig. 4 shows a flow chart of an intermediate unit for monitoring a distribution board in accordance with the present invention. The intermediate unit has, as already shown, a set of connected sensors for measuring voltage in a contactless manner. In this preferred embodiment, after the intermediate unit has been installed and configured (start) , the intermediate unit polls in a polling step 402 the sensors which parameter value corresponds to each wire, on which the respective sensors per- form measurements. In other words, the sensor is polled whether there is voltage or not . The present value of the respective sensors is acquired in an acquiring step 404 for the intermediate unit and is stored in a storing step 406 in its memory. From the memory, the present voltage values are available for acquiring the software of the server. Subsequently, a determining step 408 follows, in which it is determined whether the acquiring of values is completed or a new value is to be acquired. In normal cases, it is desirable to acquire new values, the steps 402-408 being repeated at predetermined intervals and new values overlaying previous values in the storing step 406. However, it is also possible to introduce a limitation of a predetermined number of loops, after which the acquiring is stopped. Fig. 5 shows a flow chart of a server (superordinate system) for monitoring a distribution board in accordance with the present invention. After the server has been configured (start) , the server polls the intermediate unit what current voltage values are stored (step 502) . If there is voltage across all the wires on which measurements have been performed, this step is repeated after a predetermined period of time, which conveniently is at least so long that the intermediate unit has had time to acquire new values. However, if voltage is missing across one or more of the wires on which measurements have been performed, the alarm is given in an alarm step 504, for instance to a computer or a visual display, in order to indicate in which wire or wires there is a fault . In a subsequent determining step 506, it is determined whether the loop is to be repeated or finished in accordance with pre-set settings. Even if some preferred embodiments of parts included in the system have been described above, the invention is not limited to these embodiments. As mentioned above, it is, for example, not necessary to incorporate a server in the system. The design of the alarm unit for indicating in which wire there is a fault, is also optional. Nor is there any limit to how many sensors can or should be connected to the intermediate unit, or how many wires in which it is possible to perform measurements.

It should thus be understood that several modifica- tions and variations may be provided without abandoning the scope of the present invention which is defined in the appended claims.

Claims

1. A method for monitoring a distribution board, comprising the steps of detecting, in said distribution board for at least one electric wire, in a contactless manner a characteristic binary parameter state, which can assume a first or a second value, determining the value of the binary parameter state, and determining that detection of a change of state has occurred if the value of the binary parameter state is said first value, in which case a first message about the detection is given.

2. A method for monitoring a distribution board as claimed in claim 1, in which a second message is given if detection has not occurred.

3. A method for monitoring a distribution board as claimed in claim 1 or 2 , in which the step of determining the value is preceded by the step of acquiring the value.

4. A method for monitoring a distribution board as claimed in claim 3, in which measurements are performed on a plurality of electric wires, the step of acquiring the value for the respective wires occurring from one and the same location.

5. A method for monitoring a distribution board as claimed in any one of the preceding claims, in which measurements are performed on a plurality of electric wires, and when said first value of a wire is determined, the value of the parameter state for at least one other wire is changed.

6. A method for monitoring a distribution board as claimed in any one of the preceding claims, in which said binary parameter state is a voltage across an electric wire .

7. A method for monitoring a distribution board as claimed in claim 6, in which said first message is given if there is no voltage across the electric wire.

8. A method for monitoring a distribution board as claimed in claim 6 or 7, wherein the voltage across the wire is measured in a capacitive manner.

9. A method for monitoring a distribution board as claimed in any one of claims 6-8, wherein said absence of voltage indicates a fault in at least one incoming supply main of the distribution board.

10. A method for monitoring a distribution board, as claimed in any one of claims 6-8, wherein said absence of voltage indicates a fault in at least one outgoing wire of the distribution board.

11. A method for monitoring a distribution board, as claimed in claim 9 or 10, wherein said absence of voltage indicates that at least one fuse in the distribution board has blown.

12. A method for monitoring a distribution board as claimed in claim 10, wherein said absence of voltage indicates earth fault in at least one power consuming unit connected to the distribution board.

13. A system for monitoring a distribution board which comprises electric wires, comprising

- a) at least one detecting means which is adapted to detect, in a contactless manner, a characteristic bi- nary parameter state, in a distribution board for at least one electric wire, the parameter state being able to assume a first or a second value,

- b) an intermediate unit which is arranged outside the distribution board, and with which said detecting means communicates, said intermediate unit being adapted to receive information from said detecting means and, thus, determine the value of the binary parameter state, and - c) an alarm unit, with which the intermediate unit is in communication, the alarm unit being adapted to receive the value which is determined by the intermediate unit, at least if this value is said first value, and adapted to give the alarm if the value is said first value.

14. A system as claimed in claim 13, in which the intermediate unit is adapted to poll, at predetermined intervals, said detecting means regarding the present value of the parameter state.

15. A system as claimed in claim 13 or 14, in which a plurality of detecting means are adapted to perform measurements in the distribution board, for the respec- tive electric wires, said characteristic parameter state, the intermediate unit receiving information from all the detecting means.

16. A system as claimed in claim 15, in which the intermediate unit comprises software for making conditions that, depending on the determined values, control output signals from the intermediate unit .

17. A system as claimed in claim 16, in which the intermediate unit is adapted to change the value of the parameter state for at least one wire, when the interme- diate unit has determined said first value of another wire .

18. A system as claimed in any one of claims 13-17, which further comprises a polling/conveying unit, via which the intermediate unit is in communication with the alarm unit, the polling/conveying unit being adapted to poll the intermediate unit whether the parameter state has assumed said first value and to convey this to the alarm unit .

19. A system as claimed in any one of claims 13-18, in which said detecting means comprises a sensor in order to detect, in a capacitive manner, said parameter state in the form of a voltage across the electric wire.

20. A system as claimed in claim 19, in which said sensor comprises an electrically conductive plate which is arranged, preferably fixed with tape, on insulation surrounding the electric wire, in order to detect said parameter state .

21. A system as claimed in claim 19, in which said sensor comprises an electrically conductive tape, which is fixed with tape on insulation surrounding the electric wire, in order to detect said parameter state.

22. Use of a method or a system as claimed in any one of the preceding claims, for determining whether an electric fault relates to an incoming supply main of the distribution board, or an outgoing wire of the distribution board.